Synergy of mesoporous SnO2 and RbF modification for high-efficiency and stable perovskite solar cells

Electron transport layer (ETL) is very critical to the performance of perovskite solar cells (PSCs), and optimization work on ETL has received extensive attentions especially on tin oxide (SnO2) since it is an excellent ETL material widely applied in high-efficiency PSCs. Thereinto, introducing mesoporous structure and surface modification are two important approaches which are commonly applied. Herein, based on the previous work in low-temperature fabrication process of mesoporous SnO2 (m-SnO2), we introduced a modification process with rubidium fluoride (RbF) to the m-SnO2 ETL, and successfully achieved a synergy of the m-SnO2 and RbF modification: not only the shortcoming of the m-SnO2 in interfacial traps was overcome, but also the carrier collection efficiency was further improved. The PSCs based on the m-SnO2 ETL with RbF modification demonstrated outstanding performances: a champion power conversion efficiency (PCE) of 22.72% and a stability performance of maintaining 90% of the initial PCE after 300 h of MPP tracking were obtained without surface passivation of perovskite film. Hence, utilizing the abovementioned synergy is a cost-effective and feasible strategy for fabricating high-efficiency and stable PSCs since the fabrication process of the m-SnO2 ETL is a kind of low temperature process and RbF is cheap.